Easy. First, shut down your machine. Make sure the little screw lock next to the numlock (F6) key is unlocked. Open the keyboard by pulling the spring tabs in the upper right corners of the keyboard towards you. Angle the keyboard up and out and flip it over so it is resting on the palmrest. If you have an Airport card, remove it now. Then, using a small screwdriver (#0 I think), remove the two screws holding down the metal plate that covers the memory DIMM. If you have a DIMM installed, removing it may help here. Now you'll see how the keyboard flex cable goes into the motherboard to the right of the memory slot. Do not pull up on the flex cable itself! Pull up on the black connector that plugs into the board. The keyboard you got should have this black connector already on the flex cable. If not, it would be necessary to unlock the connector from the old keyboard and attach it to the flex on the new keyboard. Now plug the new keyboard in and reverse the disassembly process. It's really pretty easy. Post if you're still having problems.
Steve